1. Field of the Invention
The present invention relates to an electromagnetic valve, in particular, applicable to a canister for processing vaporized fuel to be emitted from an automobile fuel tank.
2. Description of Related Art
Conventionally, a vehicle using gasoline as fuel has been provided with a vaporized fuel processing system for preventing vaporized fuel of a fuel tank from emitting into an air. This system has, as shown in FIG. 4, a canister 2 for adsorbing and holding vaporized fuel to be emitted from a fuel tank 4 and an electromagnetic valve 1 disposed at a air port 8 of the canister 2.
The electromagnetic valve 1 carries out a predetermined valve opening and closing operation, as shown in FIG. 5, when a leak check of the system is conducted. As shown in FIG. 8, the electromagnetic valve 1 is composed of a valve body 120 for opening and closing an air communication path 110 provided in a housing 100, a spring 130 for biasing the valve body 120 in a valve opening direction (right direction in FIG. 8) and an electromagnetic device 140 for driving the valve body 120 against a biasing force of the spring 130. The electromagnetic valve 1 is normally at a valve opening state when the electromagnetic device 140 is turned off (at a state shown in FIG. 8).
The operation of the electromagnetic valve 1 at the leak check is described below. When a built-in coil 150 of the electromagnetic device 140 is energized for leak check, a moving element 170 arranged at an internal circumference of a bobbin 160 is attracted in a left direction of the drawing. Thus, the valve body 120 is pushed out in a left direction of the drawing together with a retainer 180 assembled to the moving element 170 so that a valve opening 190 of the air communication path 110 may be closed.
When the coil 150 is de-energized to finish the leak check, the valve body 120 closing the valve opening 190 is pushed back to open the valve opening 190 by the biasing force of the spring 130, since the attracting force applied to the moving element 170 is eliminated. As a result, the valve body 120 is moved back and stopped at a predetermined position where a right side end of the retainer 180 comes in contact with a left side surface 161 of the bobbin 160.
In case of the conventional electromagnetic valve, the valve body 120 is abruptly pushed back by an elastic force stored at the spring 130 to cause the end of the retainer 180 to hit the side surface of the bobbin 160 with a hammer noise.
If the leak check is conducted during a vehicle running period when the road noises are prevailing, a generation of the hammer noise does not bring a big problem because the hammer noise can be drowned out by the road noises. However, if the leak check is conducted during a vehicle stopping period when road noises are not generated, for example, at an idling period, the generation of the hammer noise might result in a big problem because a driver hears as an abnormal and annoying sound the hammer noise not drown out by the road noises.